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& \\
\multicolumn{2}{|c|}{\LARGE\bf THE\hspace*{1cm}STAR\hspace*{1cm}FORMATION\hspace*{1cm}NEWSLETTER} \\ [0.3cm]
\multicolumn{2}{|c|}{\large\em An electronic publication dedicated to early stellar evolution and molecular clouds} \\ [0.3cm]
{\hspace*{0.8cm} No. 102 --- 1 April 2001 } & \multicolumn{1}{r|}{Editor: Bo Reipurth (reipurth@casa.colorado.edu)\hspace*{0.8cm}} \\ [-0.1cm]
& \\ \hline
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%\vspace*{1cm}
%\begin{center}
%{\Large\em From the Editor}
%\end{center}
%\vspace*{0.6cm}
\def\v3{\,{\vspace{0.3cm}}}
\def\v4{\,{\vspace{0.4cm}}}
\def\v5{\,{\vspace{0.5cm}}}
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\begin{center}
{\Large\em Abstracts of recently accepted papers}
\end{center}
\vspace*{0.6cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Two-dimensional Distributions and Column Densities of Gaseous
Molecules in Protoplanetary Disks II.---Deuterated Species and
UV Shielding by Ambient Clouds}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Y. Aikawa$^1$ and E. Herbst$^2$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Department of Earth and Planetary Sciences, Faculty of Science,
Kobe University, Kobe 657-8501, Japan} \\
$^2$ {Departments of Physics and Astronomy, The Ohio State
University, Columbus, OH 43210, USA}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: aikawa@jet.planet.sci.kobe-u.ac.jp}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
\def\lesssim{\mathrel{\hbox{\rlap{\hbox{\lower4pt\hbox{$\sim$}}}\hbox{$ 10$ magnitudes,
N$_2$H$^+$ appears relatively undepleted.
Moreover, for A$_V$ $< 4$ magnitudes there exists little or no N$_2$H$^+$.
This pattern of depletions is
consistent with the predictions of chemical theory.
Through the use of a time and depth dependent
chemical model we show that the near-uniform or rising N$_2$H$^+$ abundance with
extinction is a direct result of a reduction in
its destruction rate at high extinction due to the
predicted and observed depletion of CO molecules.
The observed abundance threshold for N$_2$H$^+$, $A_V^{th} \sim 4$ mag, is examined
in the context of this same model and we demonstrate how this technique can
be used to test the predictions of depth-dependent chemical models.
Finally, we find that cloud density gradients can have a significant effect
on the excitation and detectability of high dipole moment molecules,
which are typically far from local thermodynamic equilibrium. Density
gradients also cause chemical changes as reaction rates and
depletion timescales are density dependent. Accounting
for such density/excitation gradients is crucial to a correct determination
and proper interpretation of molecular abundances.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astrophysical Journal}
%% If preprints are available on the WWW you can give the web
%% direction here.
{Preprint available at {\tt http://xxx.lanl.gov/abs/astro-ph/0103521 or
http://cfa-www.harvard.edu/$\sim$ebergin}}
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{ISOCAM observations of the $\rho$~Ophiuchi cloud: Luminosity and
mass functions of the pre-main sequence embedded cluster}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ S. Bontemps$^{1,2}$, P. Andr\'e$^3$, A.A. Kaas$^{4,2}$, L. Nordh$^2$,
G. Olofsson$^2$, M. Huldtgren$^2$, A. Abergel$^5$, J. Blommaert$^6$,
F. Boulanger$^5$, M. Burgdorf$^6$, C.J. Cesarsky$^3$, D. Cesarsky$^5$,
E. Copet$^7$, J. Davies$^8$, E. Falgarone$^9$, G. Lagache$^5$,
T. Montmerle$^3$, M. P\'erault$^9$, P. Persi$^10$, T. Prusti$^6$,
J.L. Puget$^5$, F. Sibille$^11$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Observatoire de Bordeaux, B.P. 89, 33270 Floirac, France}\\
$^2$ {Stockholm Observatory, 133 36 Saltsj\"obaden, Sweden} \\
$^3$ {Service d'Astrophysique, CEA Saclay, 91191 Gif-sur-Yvette, France}\\
$^4$ {ESA/ESTEC, Astrophysics Division, Netherlands}\\
$^5$ {IAS, Universit\'e Paris XI, 91405 Orsay, France}\\
$^6$ {ISO/SOC, Astrophysics Division of ESA, Villafranca, Spain}\\
$^7$ {DESPA, Obs. Paris-Meudon, 5 Pl. J. Janssen, 92195 Meudon, France}\\
$^8$ {JAC, 660 N.A'Ohoku Place, University Park, Hilo, HI 96720, USA}\\
$^9$ {ENS Radioastronomie, 24 Rue Lhomond, 75231 Paris, France}\\
$^{10}$ {IAS, CNR, Area di Ricerca Tor Vergata, 00133 Roma, Italy}\\
$^{11}$ {Observatoire de Lyon, 69230 Saint Genis Laval, France}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: bontemps@observ.u-bordeaux.fr}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
\def\sm{\mbox{M$_\odot$}}
\def\sol{\mbox{L$_\odot$}}
%% Within the following brackets you place your text:
{We present the results of the first extensive
mid-infrared (IR) imaging survey
of the $\rho$~Ophiuchi embedded cluster, performed
with the ISOCAM camera on board the ISO satellite.
The main $\rho$~Ophiuchi molecular cloud L1688, as well as the two
secondary clouds L1689N and L1689S, have been completely surveyed
for point sources at 6.7~$\mu$m and 14.3~$\mu$m.
A total of 425 sources are detected in $\sim 0.7$~deg$^2$, including
16 Class~I, 123 Class~II, and 77 Class~III young stellar objects (YSOs).
Essentially all of the mid-IR sources coincide with near-IR
sources, but a large proportion of them are recognized for the first
time as YSOs. Our dual-wavelength survey allows us to identify essentially
all the YSOs with IR excess in the
embedded cluster
down to $F_\nu \sim $~10--15~mJy.
It more than doubles the known population of Class~II YSOs
and represents the most complete census to date of
newly formed stars in the $\rho$~Ophiuchi central region.
There are, however, reasons to believe that several tens of
Class~III YSOs remain to be identified below $L_\star \sim 0.2\ \sol$.
The mid-IR luminosities of most ($\sim 65$\%) Class~II objects are
consistent with emission from purely passive circumstellar disks.
The stellar luminosity function of the complete sample of Class~II
YSOs
is derived with a good accuracy down to $L_\star \sim 0.03\ \sol$.
It is basically flat (in logarithmic units)
below $L_\star \sim 2\ \sol$, exhibits a possible local maximum at
$L_\star \sim 1.5\ \sol$,
and sharply falls off at higher luminosities.
A modeling of the luminosity function, using
available pre-main sequence tracks and plausible star formation histories,
allows us to derive the mass distribution of the Class~II YSOs
which arguably reflects the initial mass function (IMF) of the
embedded cluster.
After correction for the presence of unresolved binary systems,
we estimate that the IMF in $\rho$~Ophiuchi is well described by a two-component
power law
with a low-mass index of $-0.35\pm0.25$, a high-mass index of $-1.7$
(to be compared with the Salpeter value of $-1.35$), and a break
occurring at $M_\mathrm{flat}=0.55\pm0.25\,\sm$.
This IMF is flat with
no evidence for a low-mass cutoff down to at least $\sim 0.06\,\sm$.
}
% Here you write which journal accepted your paper, for example:
{Accepted by A\&A}
%% If preprints are available on the WWW you can give the web
%% direction here.
{Available on http://xxx.lanl.gov/ (astro-ph/0103373)}
%\end{document}
\v5
{\large\bf{Formation of Planetary-Mass Objects by Protostellar Collapse
and Fragmentation}}
{\bf{ Alan P. Boss}}
{DTM, Carnegie Institution of Washington,
5241 Broad Branch Road, NW, Washington, DC 20015-1305, USA}
{E-mail contact: boss@dtm.ciw.edu}
{Searches for very low mass objects in young star clusters have uncovered
evidence for free-floating objects with inferred masses possibly as low as
5 to 15 Jupiter masses ($M_{Jup}$), similar to the masses of several
extrasolar planets. We show here that the process which forms single and
multiple protostars, namely collapse and fragmentation of molecular clouds,
might be able to produce self-gravitating objects with initial masses less
than $\sim 1 M_{Jup}$, provided that magnetic field tension effects are
important and can be represented approximately by diluting the gravitational
field. If such fragments can be ejected from an unstable quadruple
protostar system, prior to gaining significantly more mass, protostellar
collapse might then be able to explain the formation of free-floating
objects with masses below $13 M_{Jup}$. These objects might then be best
termed ``sub-brown dwarf stars''.}
{Accepted by Astrophysical Journal (Letters)}
{Preprint available at http://www.ciw.edu/boss/ftp/formff/}
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{Extended D$_2$CO emission: the smoking gun of
grain surface-chemistry}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ C.~Ceccarelli$^{1,2}$,
L.~Loinard$^{3}$,
A.~Castets$^{1}$,
A.G.G.M.~Tielens$^{4}$,
E. Caux$^{5}$,
B.Lefloch$^{2}$,
and C.Vastel$^{5}$
}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Observatoire de Bordeaux, BP 89, 33270 Floirac, France} \\
$^2$ {Laboratoire d'Astrophysique, Observatoire de Grenoble -
BP 53, F-38041 Grenoble cedex 09, France} \\
$^3$ {Instituto de Astronom\'{\i}ia, UNAM,
Apdo Postal 72-3 (Xangari), 58089 Morelia, Michoac\'an, M\'exico}\\
$^4$ {SRON, P.O. Box 800, NL-9700 AV Groningen , the Netherlands}\\
$^5$ {CESR CNRS-UPS, BP 4346, 31028 - Toulouse cedex 04, France}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: ceccarel@observ.u-bordeaux.fr}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{
We present new observations of the H$_2$CO and D$_2$CO emission
around IRAS16293-2422, a low mass protostar in the $\rho$ Ophiuchus complex.
Bright H$_2$CO and D$_2$CO emission is detected up to 40$''$ from the
center, corresponding to a linear distance of $\sim$5000 AU.
The derived H$_2$CO abundance profile has two jumps at $r \leq 150$ AU
and $r \leq 700$ AU, where the dust temperature reaches 100 K and 50 K
respectively.
The measured [D$_2$CO]/[H$_2$CO] abundance ratio in the envelope
is between 0.03 and 0.16, an extremely high value.
We demonstrate that the present new observations can only be explained if the
D$_2$CO (and H$_2$CO) are formed during the previous cold pre-collapse phase,
stored in the grain mantles, and released in the gas phase
during the pre-collapse phase.
We consider the two main competing theories for mantle formation,
i.e. pure accretion against grain surface chemistry,
and we conclude
that the former theory cannot explain the present observations,
whereas grain active chemistry very naturally does.
We found that the mantles are evaporated because of the thermal heating
of the grains by the central source and
that in the outer cold envelope H$_2$CO and D$_2$CO
molecules are embedded in CO-rich mantles which sublimate when the dust
is warmer than 25 K.
Finally, the present day H$_2$CO and D$_2$CO abundances very probably
reflect the mantle composition.
We argue that mantles have likely formed in an onion-like
structure with the innermost ice layers more enriched of H$_2$CO molecules
and we give estimates of the CO hydrogenation efficiency across the
envelope and/or in different ices.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astron. \& Astrophysics }
%% If preprints are available on the WWW you can give the web
%% direction here.
http://www-laog.obs.ujf-grenoble.fr/activites/starform/formation.html\#new2001
\v5
\def\ga{\mathrel{\hbox{\rlap{\hbox{\lower4pt\hbox{$\sim$}}}\hbox{$>$}}}}
{\large\bf{Sub-arcsecond Imaging of SiO in the HH~211 Protostellar
Jet}}
{\bf{Claire J. Chandler$^1$ and John S. Richer$^2$}}
$^1$ {National Radio Astronomy Observatory, PO Box O, Socorro, NM
87801, USA}\\
$^2$ {Department of Physics, University of Cambridge, Cavendish
Laboratory, Madingley Road, Cambridge CB3 0HE, United Kingdom}
{E-mail contact: cchandle@nrao.edu}
{We present images of the HH~211 molecular jet in the SiO $v$=0, $J$=1--0
line at 43~GHz made with the Very Large Array at approximately 0.5
arcsec resolution. The SiO emission appears to trace primarily internal
bowshocks in the outflow, suggesting that the dust and molecular gas
are accelerated via prompt entrainment at internal working surfaces in
the jet. There is also some evidence for limb-brightening of the SiO
emission, indicating that SiO emission may also arise from entrainment in
the jet's boundary layer. Excitation temperatures of $\ga 150$--200~K
are inferred from the SiO emission. Enhancements in the SiO abundance
of $\sim 10^6$ over interstellar values are observed, and the possible
origin of the SiO is discussed.}
{Accepted by ApJ}
{Preprint available at
http://www.nrao.edu/$\sim$cchandle/preprints/preprints.html}
\clearpage
{\large\bf{Multifractal Scaling, Geometrical Diversity,
and Hierarchical Structure\\
in the Cool Interstellar Medium}}
{\bf{ David Chappell and John Scalo }}
{Astronomy Dept., University of Texas, Austin, Texas 78712, USA}
{E-mail contact: parrot@astro.as.utxas.edu}
{Multifractal scaling (MFS) refers to structures that can be
described as a collection of interwoven fractal subsets which exhibit
power-law spatial scaling behavior with a range of scaling exponents
(concentration, or singularity, strengths) and dimensions. The existence of
MFS implies an underlying multiplicative (or hierarchical, or cascade)
process. Panoramic column density images of several nearby star-forming
cloud
complexes, constructed from IRAS data, are shown to exhibit such
multifractal
scaling, which we interpret as indirect but quantitative evidence for nested
hierarchical structure. The relation between the dimensions of the
subsets and their concentration strengths (the ``multifractal spectrum'')
appears to satisfactorily order the observed regions in terms of the
mixture of geometries present, from strong point-like concentrations, to
line-like
filaments or fronts, to space-filling diffuse
structures. This multifractal
spectrum is a global property of the regions studied, and does not rely on
any operational definition of ``clouds.'' The range of forms of the
multifractal spectrum among the regions studied implies that the column
density structures do not form a universality class, in contrast to
indications for velocity and passive scalar fields in incompressible
turbulence, providing another indication that the physics of highly
compressible interstellar gas dynamics differs fundamentally from
incompressible turbulence. There is no correlation between the geometrical
properties of the regions studied and their level of internal star formation
activity, a result that is also apparent from visual inspection. We discuss
the viability of the multifractal spectrum as a measure of the structural
``complexity'' of the
regions studied, and emphasize the problematic dependence of all structural
descriptors
on the subjective pre-selection of the region to be described. A comparison
of IRAS 100 $\mu$m column density (not intensity) images
with $^{13}$CO, visual extinction, and C$^{18}$O data suggests that
structural details are
captured by IRAS up to at least 30 magnitudes of visual extinction, except
in the
vicinity of embedded stars, and that lower-column density connective
structure not seen by
other methods is revealed.}
{ Accepted by The Astrophysical Journal }
Full paper available at astro-ph/9707102
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{Observations of Molecular Clouds in the HH 270/110 Region}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{Minho Choi$^{1 2}$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Institute of Astronomy and Astrophysics, Academia Sinica,
Nankang P.O. Box 1-87, Taipei 11529, Taiwan} \\
$^2$ {Department of Astronomy, University of Maryland,
College Park, MD 20742, USA}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: minho@asiaa.sinica.edu.tw}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{We present the millimeter continuum and molecular line observations
of the middle condensation of the L1617 cloud.
Various molecular structures were found
in the HCO$^+$ and the HCN lines.
The driving source of the HH 270 flow was detected in the continuum
and is surrounded by a flattened dense molecular core
with possible infall motion.
The HCO$^+$ and the HCN emission at the ambient cloud velocity
are enhanced along the HH 270 jet axis,
but the molecular clumps do not show a kinematic sign of outflow.
The enhancement could be caused by irradiation from shocks.
In the immediate vicinity of HH 110A, the northernmost knot of HH 110,
neither a continuum source
nor any evidence of jet-cloud collision was found.
To the west of HH 110, there is a filamentary structure of dense gas
which contains at least two outflow sources.
The driving source of the IRS 2 jet was detected in the continuum.}
% Here you write which journal accepted your paper, for example:
{Accepted by the Astrophysical Journal}
%% If preprints are available on the WWW you can give the web
%% direction here.
{Preprint: http://www.asiaa.sinica.edu.tw/minho/pubs/}
%\end{document}
\clearpage
%% Between these brackets you write the title of your paper:
{\large\bf{A Submillimeter Study of the Star-Forming Region NGC 7129}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{Andreea S. Font$^1$,$^2$ George F. Mitchell$^1$ \ and G\"oran Sandell$^3$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Department of Astronomy and Physics, Saint Mary's University, Halifax, NS, B3H 3C3, Canada} \\
$^2$ {Present address: Department of Physics and Astronomy, University of Victoria, P.O Box 3055, Victoria, B.C., V8W 3P6, Canada.} \\
$^3$ {USRA, NASA Ames Research Center, MS 144-2, Moffett Field, CA 94035, U.S.A.}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: gsandell@mail.arc.nasa.gov, afont@noir.phys.uvic.ca}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
\newcommand{\mic}{\mbox{\,${\mu}$m}}
%% Within the following brackets you place your text:
{New molecular ($^{13}$CO J=3$-$2) and dust continuum (450\mic\ and 850\mic) maps of the NGC7129 star forming region are presented. The maps include the Herbig Ae/Be star LkH$\alpha$ 234, the far-infrared source NGC 7129 FIRS2 and several other pre-stellar sources embedded within the molecular ridge. The data are complemented with C$^{18}$O J=3$-$2 spectra at several positions within the mapped region.
Both the submillimeter and the $^{13}$CO emission show a similar morphology, displaying a sharp boundary towards the cavity. The submillimiter maps also reveal a second source, SMM\,2, which is not clearly seen in any earlier data set. This is either a pre-stellar core or possibly a protostar. Also, the highest continuum peak emission is identified with the deeply embedded source IRS\,6 a few arcseconds away from LkH$\alpha$ 234. These new 450 and 850\mic\ observations are combined with previous continuum observations of the three compact far-infrared sources in the field, in order to make fits to the spectral energy distributions and to obtain the source sizes, dust temperatures, luminosities, and masses. For nine positions where both $^{13}$CO and C$^{18}$O spectra are available, gas masses have been obtained and compared with masses derived from the continuum fluxes. The masses are found to be consistent, implying little or no CO depletion onto grains. The dust emissivity index is found to be low towards the dense compact sources, $\beta$ $\sim$1 $-$ 1.6, and high, $\beta$ $\sim$ 2.0, in the surrounding cloud.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astrophysical Journal}
%% If preprints are available on the WWW you can give the web
%% direction here.
%\end{document}
\vspace{0.3cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Proper Motion of the EHV SiO $J$=2$\to$1 Emission in L1448}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{Jos\'e M. Girart$^1$ \ and Jerry M. P. Acord$^2$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Department of Astronomy, University of Illinois,
1002 W. Green Street, Urbana, IL 61801, USA} \\
$^2$ {Syncretic Software Inc., 650 Naamans Rd, Suite 209B,
Claymont, DE 19703, USA}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: jgirart@am.ub.es}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
\newcommand{\kms} {~km~s$^{-1}$}
\newcommand{\J}[2] {\mbox{$J$=#1$\to$#2}}
%% Within the following brackets you place your text:
{We report the first measurements of proper motions in a molecular outflow
by using interferometric rotational line observations. We observed and
mapped with the BIMA (Berkeley Illinois Maryland Association) millimeter
array the extremely high velocity (EHV) SiO \J{2}{1}\ emission associated
with the L1448 molecular outflow. Comparisons were made with the Plateau
de Bure (PdB) interferometer maps carried out 8.5 years earlier. We
obtained proper motions of up to $0.12''$~yr$^{-1}$, which imply
absolute velocities of 180~\kms\ and an outflow inclination of $21^{\circ}$
to the plane of the sky, in agreement with previous modeling of the CO
emission. These proper motions suggests that the EHV emission in L1448
has a short time scale. These results strongly suggest that with the new
generation of powerful interferometric arrays the combination of high
spectral and angular resolution with high sensitivity will permit a
detailed 3-D picture of the kinematics of molecular outflows.}
% Here you write which journal accepted your paper, for example:
{ Accepted by ApL Letters }
%% If preprints are available on the WWW you can give the web
%% direction here.
www.am.ub.es/$\sim$jgirart/curro.html
%\end{document}
\vspace{0.3cm}
%% Between these brackets you write the title of your paper:
{\large\bf
{ Barnard's Merope Nebula Revisited: New Observational Results} }
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ G. H. Herbig and Theodore Simon } }
%% Here you write your institute name(s) and address(es),
{ Institute for Astronomy, University of Hawaii,
2680 Woodlawn Drive, Honolulu, HI 96822, U.S.A.}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: herbig@galileo.ifa.hawaii.edu}
%% Within the following brackets you place your text:
{ IC 349 is a small, fan-shaped reflection nebula located only 30$''$
from 23 Tau; its nucleus is by a factor 15 the brightest area of the Pleiades
nebulosity. We propose that IC 349 is a fragment of the Tau-Aur molecular
cloud that has been encountered by the Pleiades in that cluster's southward
motion, and is being illuminated and shaped by the radiation field of 23 Tau.
New HST multicolor imagery, and the structure, colors and surface brightness of
IC 349 are discussed in terms of that hypothesis. What is known of the space
motion of the nebula (obtained from the molecular-line radial velocity of the
Taurus clouds and proper motions of the T Tauri stars therein),
what can be inferred for the properties of the nebula from its color, and
what is expected from radiation pressure theory appear to be compatible with
this cloudlet-encounter hypothesis. }
% Here you write which journal accepted your paper, for example:
{ Accepted by Astron. J., June 2001 issue }
%% If preprints are available on the WWW you can give the web
%% direction here.
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{Search for low-mass PMS companions around X-ray selected
late B stars}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ S. Hubrig$^1$, D. Le Mignant$^2$, P. North$^3$ \ and J. Krautter$^4$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {European Southern Observatory, Casilla 19001, Santiago 19, Chile} \\
$^2$ {W. M. Keck Observatory, 65-1120 Mamalahoa Highway, Kamuela. HI 96743,
USA} \\
$^3$ {Institut d'Astronomie de l'Universit\'e de Lausanne, CH-1290
Chavannes-des-Bois, Switzerland}\\
$^4$ {Landessternwarte Heidelberg-K\"onigstuhl, D-69117 Heidelberg, Germany}\\
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: shubrig@eso.org}
%% Within the following brackets you place your text:
{We have observed 49 X-ray detected bright late B-type dwarfs to search for
close low-mass pre-main sequence (PMS) companions using the European Southern
Observatory's ADONIS (Adaptive Optics Near Infrared System) instrument.
We announce the discovery of 21 new companions in 9 binaries, 5 triple,
4 quadruple system and 1 system consisting of five stars.
The detected new companions have K magnitudes
between 6$^{\rm m}.$5 and 17$^{\rm m}.$3 and angular separations ranging from
0.''2 and 14.''1 (18-2358 AU).}
% Here you write which journal accepted your paper, for example:
{ Accepted by A \& A}
%% If preprints are available on the WWW you can give the web
%% direction here.
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{$K$ band Spectroscopy of Luminous Young Stellar Objects}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Miki Ishii$^1$, Tetsuya Nagata$^1$ Shuji Sato$^1$,
Yongqiang Yao$^2$, Zhibo Jiang$^2$, \ and Hidehiko Nakaya$^3$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Department of Astrophysics, Nagoya University, Furo-cho,
Chikusa-ku, Nagoya 464-8602, Japan} \\
$^2$ {Purple Mountain Observatory, National Astronomical Observatories,
Chinese Academy of Sciences, Nanjing 210008, China} \\
$^3$ {Subaru Telescope, NAOJ, 650 North A'ohoku Place, Hilo, HI 96720
U.S.A.}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: ishii@z.phys.nagoya-u.ac.jp}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{We present the spectroscopy
from 2.0 to 2.33 $\mu$m of 32 luminous
Young Stellar Objects (YSOs)
which are presumed to be precursors of Herbig Ae/Be stars.
From these stars, Br$\gamma$, H$_2$, CO, HeI,
and FeII were found in emission
with the detection rate of
97 \%, 34 \%, 22 \%, 9 \% and 3 \%, respectively.
We compared the spectral features with those
of Herbig Ae/Be stars in the literature to investigate the
spectral behavior of intermediate- to high-mass YSOs,
and to search for their relations to the
Spectral Energy Distributions (SEDs).
H$_2$ emission is detected only in Class~I SEDs
with particularly large spectral indices.
The detection of H$_2$ emission
is related to the degree of the dispersal of
circumstellar envelopes where H$_2$ molecules are
probably excited by shocks from outflows.
On the other hand, Br$\gamma$ emission, which is generally
thought to occur in stellar wind close to the stars,
does not depend on the SEDs.
This indicates that stellar wind from luminous YSOs does
not change much from the embedded phase to the
optically visible phase.
CO emission is also independent of the SEDs,
but the detection rate is much lower
than that of Br$\gamma$ emission.
Probably more strict physical conditions of
circumstellar disks and stellar radiation are
necessary for CO emission to take place. }
% Here you write which journal accepted your paper, for example:
{ Accepted by Astron.\ J. June 2001 (Vol.\ 121, No.\ 4) }
%% If preprints are available on the WWW you can give the web
%% direction here.
%\end{document}
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{The Formation of Stellar Clusters: Time Varying Protostellar
Accretion Rates}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Ralf S.\ Klessen$^1$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {UCO/Lick Observatory, University of California at Santa Cruz,
499 Kerr Hall, Santa Cruz, CA 95064, U.S.A.}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: ralf@ucolick.org}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{ Identifying the processes that determine strength, duration and
variability of protostellar mass growth is a fundamental ingredient
of any theory of star formation. I discuss protostellar mass
accretion rates $\dot{M}$ from numerical models which follow
molecular cloud evolution from turbulent fragmentation towards the
formation of stellar clusters. In a dense cluster environment,
$\dot{M}$ is strongly time varying and influenced by the mutual
interaction of protostellar cores and their competition for
accretion from the common cluster gas reservoir. Even for protostars
with similar final mass, the accretion histories may differ
dramatically. High-mass stars build up in the central parts of
dense, cluster-forming cloud regions. They begin to form in the
early phases of cluster evolution, and continue to grow at a high
rate until the available gas is exhausted or expelled by feedback.
Lower-mass stars tend to form at later phases, and $\dot{M}$
declines rapidly after a short initial phase of strong growth. I
present a simple fit formula for the time evolution of the average
$\dot{M}$ for protostars of different masses in a dense cluster
environment.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by ApJ Letters }
%% If preprints are available on the WWW you can give the web
%% direction here.
Preprint available at
http://www.ucolick.org/~ralf/Preprints/p11.abstract.html
%\end{document}
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{On the origin of the distribution of binary-star periods}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Pavel Kroupa$^1$ \ and Andreas Burkert$^2$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Institut f\"ur Theoretische Physik und Astrophysik, Universit\"at
Kiel, D-24098 Kiel, Germany}\\
$^2$ {Max-Planck-Institut f\"ur Astronomie, K\"onigstuhl 17,
D-69117 Heidelberg, Germany}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: pavel@astrophysik.uni-kiel.de; burkert@mpia-hd.mpg.de}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{
Pre-main sequence and main-sequence binary systems are observed to
have periods, $P$, ranging from one day to $10^{10}$~days and
eccentricities, $e$, ranging from~0 to~1. We pose the problem if
stellar-dynamical interactions in very young and compact star clusters
may broaden an initially narrow period distribution to the observed
width. $N$-body computations of extremely compact clusters
containing~100 and~1000 stars initially in equilibrium and in cold
collapse are preformed. In all cases the assumed initial period
distribution is uniform in the narrow range $4.5\le\,{\rm
log}_{10}P\le 5.5$ ($P$ in days) which straddles the maximum in the
observed period distribution of late-type Galactic-field dwarf
systems. None of the models lead to the necessary broadening of the
period distribution, despite our adopted extreme conditions that
favour binary--binary interactions. Stellar-dynamical interactions in
embedded clusters thus cannot, {\it under any circumstances}, widen
the period distribution sufficiently. The wide range of orbital
periods of very young and old binary systems is therefore a result of
cloud fragmentation and immediate subsequent magneto-hydrodynamical
processes operating within the multiple proto-stellar system.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by ApJ }
%% If preprints are available on the WWW you can give the web
%% direction here.
http://xxx.lanl.gov/abs/astro-ph/0103429
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{Doubly deuterated molecular species in protostellar
environments}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Laurent Loinard$^1$, A.Castets$^2$, C.Ceccarelli$^{2,3}$,
E.Caux$^4$ \ and
A.G.G.M. Tielens$^5$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {IA/UNAM, Apdo Postal 72--3 (Xangari), 58089 Morelia, Michoac\'an,
M\'exico} \\
$^2$ {Observatoire de l'Universit\'e de Bordeaux I, B.P. 89,
F-33270 Floirac, France} \\
$^3$ {LAOG, B.P. 53, F-38041 Grenoble Cedex 09, France}\\
$^4$ {CESR, CNRS-UPS, B.P. 4346, 31028 Toulouse Cedex 04, France}\\
$^5$ {SRON, P.O. Box 800, 9700 AV Groningen, The Netherlands}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: l.loinard@astrosmo.unam.mx}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
\newcommand{\dtco}{D$_{2}$CO}
\newcommand{\Htwo}{H$_{2}$}
\newcommand{\hdco}{HDCO}
\newcommand{\htco}{H$_{2}$CO}
\newcommand{\httco}{H$_{2}$$^{13}$CO}
\newcommand{\dttco}{D$_{2}$$^{13}$CO}
\newcommand{\nhtd}{NH$_{2}$D}
\newcommand{\ndth}{ND$_{2}$H}
\newcommand{\nht}{NH$_{3}$}
%% Within the following brackets you place your text:
{We report the detection of the doubly deuterated forms of ammonia
(ND$_2$H) and formaldehyde (D$_2$CO) towards 16293E, a newly
identified low--luminosity protostar in the $\rho$--Ophiucus molecular
complex. The abundances of ND$_2$H and D$_2$CO compared to their
hydrogenated counterparts NH$_3$ and H$_2$CO are $\sim$ 3 \% and 40
$\pm$ 20 \%, respectively. To date, 16239E is thus the source with the
highest levels of multiple deuteration: [\ndth]/[\nht] is 5 to 6 times
larger there than in the only other astronomical source where \ndth\
has ever been found: the dense ammonia core of L134N; and
[\dtco]/[\htco] is more than 5 times higher than in the proto--binary
system IRAS16293--2422. The relative abundances of doubly deuterated
molecules in low--luminosity protostars is much higher than their
current gas--phase [D]/[H] ratio would suggest; and, therefore, likely
reflect active grain surface chemistry followed by some desorption
process.}
% Here you write which journal accepted your paper, for example:
{ Accepted by the Astrophysical Journal Letters}
%% If preprints are available on the WWW you can give the web
%% direction here.
http://www.astrosmo.unam.mx/~l.loinard/publi.html
%\end{document}
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{The kinematics of molecular clumps surrounding hot cores in
G29.96$-$0.02 and G31.41$+$0.31}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{C. Maxia$^{1,2}$, L. Testi$^3$, R. Cesaroni$^3$, C.M. Walmsley$^3$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Osservatorio Astronomico di Cagliari, Str. 54, Loc. Poggio dei Pini,
I-09012 Capoterra (CA), Italy}\\
$^2$ {Dipartimento di Scienze Fisiche, Universit\`a di Cagliari, Cittadella
Universitaria, I-09042 Monserrato (CA), Italy}\\
$^3$ {Osservatorio Astrofisico di Arcetri,
Largo E. Fermi 5, I-50125 Firenze, Italy}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: cmaxia@ca.astro.it, lt@arcetri.astro.it}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
\def\gv{{G29.96$-$0.02}}
\def\gt{{G31.41$+$0.31}}
%% Within the following brackets you place your text:
{
We present high angular resolution interferometric
observations of
the 3 and 1.3~mm continuum emission, and HCO$^+$(1--0)
and SiO(2--1)~v=0 lines,
obtained with the Owens Valley Radio Observatory millimeter-wave array,
toward two hot cores (HCs) associated with two well known ultracompact
(UC) HII regions: \gv\ and \gt. These HCs
are believed to host young forming massive stars which have been suggested
to be surrounded by massive rotating accretion disks.
The aim of these new observations
is to study the structure and kinematics of the molecular clumps surrounding
the HCs and nearby UC~HII regions at moderately high angular resolution.
Our observations reveal that the clumps within which the
HCs and UC~HII regions are embedded have
a complex kinematical structure. The total mass
of the clumps is estimated to be in the range 1000--3000~$M_\odot$,
consistent with
previous findings.
Our observations also show compelling evidence that the clump in
\gv\ is contracting onto the HC position,
suggesting that the accretion
process onto the massive young stellar object embedded in the HC is still
ongoing. In these objects the kinematical structure that we observe is also
compatible with
the presence of a massive rotating disk within the HC,
even though we cannot prove this suggestion with our data.
The case of \gt\ is more complicated, and our data, although
consistent with the presence of an inner disk and an infalling envelope around
it, do not have the required spatial resolution to resolve the different structu
res.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by A\&A}
%% If preprints are available on the WWW you can give the web
%% direction here.
http://www.arcetri.astro.it/$\sim$lt/preprints/preprints.html
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{Submillimeter Imaging Polarimetry of the NGC 7538 Region}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ M. Momose$^1$, M. Tamura$^2$, O. Kameya$^{2,3}$,
J. S. Greaves$^4$, A. Chrysostomou$^{4,5}$, J. H. Hough$^5$,
\& J. -I. Morino$^6$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Institute of Astrophysics and Planetary Sciences,
Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512, Japan} \\
$^2$ {National Astronomical Observatory of Japan, Osawa, Mitaka,
Tokyo 181-8588, Japan} \\
$^3$ {Mizusawa Astrogeodynamics Observatory, Mizusawa,
Iwate 023-0861, Japan} \\
$^4$ {Joint Astronomy Centre, 660 North A`oh\=ok\=u Place,
University Park, Hilo, HI 96720, USA} \\
$^5$ {Department of Physical Sciences, University of
Hertfordshire, Hatfield, Hertfordshire AL10 9AB, UK.} \\
$^6$ {Nobeyama Radio Observatory, Nobeyama, Minamisaku, Nagano
384-1305, Japan}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: momose@mito.ipc.ibaraki.ac.jp}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{Imaging polarimetry of the 850 $\mu$m continuum emission
in the NGC 7538 region, obtained with the SCUBA Polarimeter, is
presented. The polarization map is interpreted in terms of
thermal radiation by magnetically aligned dust grains. Two
prominent cores associated with IRS 1 and IRS 11, IRS 1(SMM) and IRS 11(SMM),
are found in the surface brightness map. Although these cores look
similar in surface brightness, their polarization shows striking
differences. In IRS 11(SMM), the polarization vectors are extremely well
ordered, and the degrees of polarization are quite high with an average
of $\sim$3.9 \%. In IRS 1(SMM), on the other hand, the directions of
polarization vectors are locally disturbed, and the degrees of
polarization are much lower than those of IRS 11(SMM). These differences
suggest that small scale fluctuations of the magnetic field are more
prominent in IRS 1(SMM). This can be interpreted in terms of the difference
in evolutionary stage of the cores. Inside IRS 1(SMM), which seems
to be at a later evolutionary stage than IRS 11(SMM), substructures such
as subclumps or a cluster of infrared sources have already
formed. Small scale fluctuations in the magnetic field could have
developed during the formation of these substructures.
The distribution of magnetic field directions derived from our
polarization map agrees well with those of molecular outflows
associated with IRS 1(SMM) and IRS 11(SMM). Comparisons of energy
densities between
the magnetic field and the outflows show that the magnetic field
probably plays an important role in guiding the directions of the outflows.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by ApJ. }
%% If preprints are available on the WWW you can give the web
%% direction here.
astro-ph/0103334, http://stars.sci.ibaraki.ac.jp/$^{\sim}$momose/publication.html
%\end{document}
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{Infrared and Millimetric Study of the Young Outflow Cepheus E}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{Amaya Moro-Mart\'{\i}n$^1$, Alberto Noriega-Crespo$^2$,
Sergio Molinari$^3$, Leonardo Testi$^4$, Jos\'e Cernicharo $^5$
\& Anneila Sargent$^6$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Steward Observatory, University of Arizona, Tucson, AZ 85721, USA} \\
$^2$ {SIRTF Science Center, California Institute of Technology,
Pasadena, CA 91125, USA} \\
$^3$ {Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125, USA} \\
$^4$ {Osservatorio Astrofisico di Arcetri, 50125 Firenze, Italy} \\
$^5$ {Instituto de Estructura de la Materia, CSIC, Calle Serrano 40, Madrid, Spain} \\
$^6$ {Division of Physics, Mathematics and Astronomy, California Institute of Technology,Pasadena, CA 91125, USA}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
%%
\vspace*{0.2cm}
{E-mail contact: amaya@as.arizona.edu}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
\def \kms{km~$\rm{s}^{-1}$}
\def \mum{$\mu$m}
%% Within the following brackets you place your text:
{The Cepheus E outflow has been studied in the mid and far infrared using
the ISO CAM and LWS instruments, and at millimetric wavelengths
using OVRO. In the near and mid-IR, its morphology is similar to that
expected for a jet driven outflow, where the leading bow shocks entrain
and accelerate the surrounding molecular gas. As expected,
fine structure atomic/ionic emission lines arise from the
bow shocks, at both the Mach Disk and the stagnation tip,
where J-shocks are dominant. The H$_2$, H$_2$O and CO molecular emission
could arise further `downstream' at the bow shock wings where the shocks
(v = $8 - 35$ \kms) are oblique and more likely to be C-type.
The $^{13}$CO emission arises from entrained molecular gas and a compact
high velocity emission is observed, together with
an extended low velocity component that {\it almost} coincides spatially
with the H$_2$ near-IR emission. The millimetric continuum emission shows
two sources. We identify one of them with IRAS 23011+6126, postulating
is the driver of the Cepheus E outflow; the other, also an
embedded source, is likely to be driving one of other outflows observed in
the region.
Finally, we suggest that the strong [C~II] 158~\mum~emission must originate
from an extended photo-dissociation region, very likely excited by the nearby
Cepheus OB3 association.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astrophys. J. }
%% If preprints are available on the WWW you can give the web
%% direction here.
http://arXiv.org/abs/astro-ph/0103065
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{A reconsideration of disk properties in Herbig Ae stars}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{
A. Natta$^1$, T. Prusti$^2$,
R. Neri$^3$, D. Wooden$^4$, V.P. Grinin$^{5,6}$,
and V. Mannings$^7$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ { Osservatorio Astrofisico di Arcetri, Largo E.Fermi 5,
I-50125 Firenze, Italy
} \\
$^2$ {
Astrophysics Division, Space Science Department of ESA,
ESTEC, P.O. Box 299, 2200 AG Noordwijk, The Netherlands} \\
$^3$ {IRAM, 300 Rue de la Piscine, Domaine Universitaire,
F-38406 St. Martin d'H\`eres Cedex, France }
$^4${NASA-Ames Research Center, Moffett Field, CA 94035, USA}\\
$^5${Crimean Astrophysical Observatory, Crimea, 334413 Nauchny, Ukraine
}\\
$^6${St. Petersburgh University, St. Petersburgh, 198904, Russia}\\
$^7${SIRTF Science Center, California Institute of Technology, MS 314-6, Pasadena, CA 91125, USA}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: natta@arcetri.astro.it}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
\newcommand {\um}{$\mu$m}
%% Within the following brackets you place your text:
{
This paper presents state-of-the-art spectral energy distributions
(SEDs) of four Herbig Ae stars, based in part on new data
in the mid and far-infrared and at millimeter wavelengths.
The SEDs are discussed in the context of circumstellar disk
models. We show that models of irradiated disks provide a good
fit to the observations over the whole range of wavelengths.
We offer a possible solution to the long-standing puzzle caused by
the excess emission of Herbig Ae stars, where
a large fraction of the stellar luminosity is re-radiated
between $\sim$1.25 and 7 \um, with a peak
at about 3 \um. We suggest that this general behaviour
can be caused by dust evaporation in disks where the gas component
is optically thin to the stellar radiation, as expected if the
accretion rate is very low. The creation of a puffed-up inner wall
of optically thick dust at the dust sublimation radius can account
for the near-infrared characteristics of the SEDs. It can also
naturally explain the H and K band interferometric observations
of AB Aur (Millan-Gabet et al. 2001), which reveal a ring of emission
of radius $\sim$0.3 AU.
Finally, irradiated disk models can easily explain the observed
intensity of the 10 \um\ silicate features and their variation
from star to star.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astron. Astrophys. }
%% If preprints are available on the WWW you can give the web
%% direction here.
available at http://www.arcetri.astro.it/$\sim$starform/publ2001.htm
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{\emph{FUSE} and HST/STIS Observations of Hot and Cold
Gas in the AB Aurigae System}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ A.~Roberge$^{1}$, A.~Lecavelier des Etangs$^{2}$,
C.~A.~Grady$^{3}$, A.~Vidal-Madjar$^{2}$, J.-C.~Bouret$^{3}$,
P.~D.~Feldman$^{1}$, M.~Deleuil$^{4}$, M.~Andre$^{1}$, A.~Boggess$^{5}$,
F.~C.~Bruhweiler$^{5}$, R.~Ferlet$^{2}$, and B.~Woodgate$^{3}$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Department of Physics and Astronomy, Johns Hopkins University,
3400 N. Charles St., Baltimore, Maryland 21218, USA} \\
$^2$ {Institut d'Astrophysique de Paris, CNRS, 98bis Bd Arago,
F-75014 Paris, France} \\
$^3$ {NASA/Goddard Space Flight Center, Code 685, Greenbelt, Maryland 20771} \\
$^4$ {Laboratoire d'Astronomie de Marseille, BP 8, F-13376
Marseille Cedex 12, France} \\
$^5$ {Institute for Astrophysics \& Computational Sciences,
Department of Physics, 200 Hannan Hall, Catholic University of America,
Washington, DC 20064, USA}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: akir@pha.jhu.edu}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%\newcommand{\Os}{\ion{O}{6}}
%\newcommand{\Ct}{\ion{C}{3}}
\newcommand{\hh}{H$_{2}$}
%\newcommand{\N}{\ion{N}{1}}
%% Within the following brackets you place your text:
{We present the first observations of a Herbig Ae star with a
circumstellar disk by the \emph{Far Ultraviolet Spectroscopic Explorer}
(\emph{FUSE}), as well as a simultaneous observation of the star obtained
with the \emph{Hubble Space Telescope} Space Telescope Imaging
Spectrograph (STIS).
The spectra of AB Aurigae show emission and absorption features
arising from gasses that have a wide range in temperature, from hot OVI
emission to cold \hh\ and CO absorption. Emissions from the
highly ionized species OVI and CIII present in the \emph{FUSE} spectrum
are redshifted, while absorption features arising from
low-ionization species like OI, NI, and SiII are
blueshifted and show characteristic stellar wind line-profiles.
We find the total column density of \hh\ toward AB Aur from the \emph{FUSE}
spectrum, $N(\rm{H}_2) = (6.8 \pm 0.5) \times 10^{19}$ cm$^{-2}$.
The gas kinetic temperature of the \hh\ derived from the ratio
$N(J=1)/N(J=0)$ is $65 \pm 4$ K. The column density of the CO observed
in the STIS spectrum is $N(\rm{CO}) = (7.1 \pm 0.5) \times 10^{13}$
cm$^{-2}$, giving a CO$/$\hh\ ratio of $(1.04 \pm 0.11) \times 10^{-6}$.
We also use the STIS spectrum to find the column density of HI,
permitting us to calculate the total column density of hydrogen atoms,
the fractional abundance of \hh, and the gas-to-dust ratio.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astrophysical Journal Letters }
%% If preprints are available on the WWW you can give the web
%% direction here.
http://arXiv.org/abs/astro-ph/0103084
%\end{document}
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{New models of interstellar gas-grain chemistry. III. Solid
CO$_{2}$.}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{Deborah P. Ruffle$^{1*}$ \ and Eric Herbst $^{2}$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^{1}$Department of Physics, The Ohio State University, Columbus,
Ohio 43210, USA \\
$^{2}$Departments of Physics and Astronomy, The Ohio State
University, Columbus,
Ohio 43210, USA \\
$^{*}$Current Address: School of Chemistry, University of Leeds,
Leeds LS2 9JT, UK
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: dpr@ast.leeds.ac.uk; herbst@mps.ohio-state.edu}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{ Solid carbon dioxide is observed to be an abundant interstellar
ice component towards both quiescent clouds and active
star-forming regions. Our recent models of gas-grain chemistry,
appropriate for quiescent regions, severely underproduce solid
CO$_{2}$ at the single assumed gas density and temperature. In
this paper, we investigate the sensitivity of our model results to
changes in these parameters. In addition, we examine how the
nature of the grain surface affects the results and also consider
the role of the key surface reaction between O and CO. We conclude
that the observed high abundance of solid CO$_{2}$ can be reproduced
at reasonable temperatures and densities by models with diffusive
surface chemistry, provided that diffusion of heavy species such
as O occurs efficiently. }
% Here you write which journal accepted your paper, for example:
{ Accepted by MNRAS }
%% If preprints are available on the WWW you can give the web
%% direction here.
\clearpage
{\large\bf{Aromatic Hydrocarbons, Diamonds, and Fullerenes
in Interstellar Space:
Puzzles to be Solved by Laboratory and Theoretical
Astrochemistry }}
{\bf{ K. Sellgren$^1$ }}
$^1$ {Astronomy Department, Ohio State University}
{E-mail contact: sellgren@astronomy.ohio-state.edu}
{New research is presented, and previous research is reviewed,
on the emission and absorption of interstellar aromatic hydrocarbons.
Emission from aromatic hydrocarbons dominate the
mid-infrared emission of many galaxies,
including our own Milky Way galaxy.
Only recently have aromatic hydrocarbons been observed in absorption
in the interstellar medium, along lines of sight with high column densities
of interstellar gas and dust.
Much work on interstellar aromatics has been done, with astronomical
observations and laboratory and theoretical astrochemistry.
In many cases the predictions of laboratory and theoretical work are
confirmed by astronomical observations, but in other cases clear discrepancies
exist which provide problems to be solved by a combination of astronomical
observations, laboratory studies, and theoretical studies.
The emphasis of this paper will be on current outstanding puzzles
concerning aromatic hydrocarbons which
require further laboratory and theoretical astrochemistry to resolve.
This paper will also touch on related topics where
laboratory and theoretical astrochemistry studies are needed to
explain astrophysical observations, such as a
possible absorption feature due to interstellar ``diamonds'' and the
search for fullerenes in space. }
{ Accepted by Spectrochimica Acta Part A: Molecular \& Biomolecular
Spectroscopy}
http://www.astronomy.ohio-state.edu/~sellgren/saa.html
or
http://xxx.lanl.gov/abs/astro-ph/0010138
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{Dusty Debris Around Solar-Type Stars: Temporal Disk Evolution}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ C. Spangler$^1$, A.I. Sargent$^1$, M.D. Silverstone$^2$, E.E.
Becklin$^2$ \ and B. Zuckerman$^2$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Division of Physics, Mathematics and Astronomy, California Institute
of Technology, MS~105-24, Pasadena, CA 91125, USA} \\
$^2$ {Division of Astronomy and Astrophysics, University of California,
Los~Angeles, Los~Angeles, CA 90095-1562, USA}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: celeste@spanglers.com}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{ Using ISO-ISOPHOT we carried out a survey of almost 150 stars to search
for
evidence of emission from dust orbiting young main sequence stars, both in
clusters and isolated systems. Over half of the detections are new
examples
of dusty stellar systems, and demonstrate that such dust can be detected
around numerous stars older than a few $\times 10^6$~years. Fluxes at
60\,$\mu$m and either 90 or 100\,$\mu$m for the new excess sources
together with improved fluxes for a number of IRAS-identified sources are
presented. Analysis of the excess luminosity relative to the stellar
photosphere shows a systematic decline of this excess with stellar age
consistent with a power law index of $-2$.}
% Here you write which journal accepted your paper, for example:
{ Accepted by ApJ }
%% If preprints are available on the WWW you can give the web
%% direction here.
{preprints available at:
http://www.arXiv.org/abs/astro-ph/0103185 }
%\end{document}
\v5
%% Between these brackets you write the title of your paper:
{\large\bf Circumstellar structure of RU Lupi down to au scales{}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{M. Takami$^1$, J. Bailey$^2$, T.M. Gledhill$^1$, A. Chrysostomou$^1$ and J.H. Hough$^1$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Department of Physical Sciences, University of
Hertfordshire, Hatfield, Herts AL10 9AB, UK.} \\
$^2$ {Anglo-Australian Observatory, PO Box 296, Epping, NSW 1710, Australia}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: takami@star.herts.ac.uk}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{We have used the technique of spectro-astrometry to study the milli-arcsecond
scale structure of the emission lines in the T Tauri star RU Lupi. The wings of
the H$\alpha$ emission are found to be displaced from the star towards the
south-west (blue wing) and north-east (red wing) with angular scales of 20-30
milli-arcsecs. This structure is consistent with a bipolar outflow from the
star.
From a study of the variability of the intensity and position spectra
we argue that a combination of magnetically-driven bipolar outflow and
accreting gas contribute to the H$\alpha$ emission.
On the other hand,
the [OI] and [SII] emission are displaced from the star to the south-west
but at much larger distances than the H$\alpha$, hundreds of milli-arcsecs
for the high-velocity component (HVC) and down to 30 milli-arcsecs for
the low-velocity components (LVC).
The presence of both red-shifted and blue-shifted outflows in H$\alpha$ but
only a blue-shifted outflow in the forbidden lines can be explained if the
disc obscures the red-shifted forbidden line outflow, but a disc gap with outer
radius 3-4 au allows the red-shifted H$\alpha$ to be seen. This gap could be
induced by an unseen companion.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by MNRAS }
%% If preprints are available on the WWW you can give the web
%% direction here.
http://arXiv.org/abs/astro-ph/0103311
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{The Stellar Composition of the Star Formation Region CMa R1 --
II. Spectroscopic and Photometric Observations of 9 Young Stars}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ H.R.E. Tjin A Djie$^1$, M.E. van den Ancker$^2$, P.F.C. Blondel$^1$,
V.S. Shevchenko$^3$, O.V. Ezhkova$^3$, D. de Winter$^4$ and
K.N. Grankin$^3$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Astronomical Institute, University of Amsterdam,
Kruislaan 403, 1098 SJ Amsterdam, The Netherlands} \\
$^2$ {Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 42,
Cambridge MA 02138, USA} \\
$^3$ {Astronomical Institute of the Academy of Sciences of Uzbekistan,
Astronomicheskaya 33, Tashkent 700052, Uzbekistan} \\
$^4$ {TNO-TPD, Stieltjesweg 1, P.O. Box 155, 2600 AD Delft, The Netherlands}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc, for example:
{E-mail contact: herman@astro.uva.nl}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
\def\mag{\hbox{$^{\rm m}$}}
%% Within the following brackets you place your text:
{
We present new high and low resolution spectroscopic and photometric data
of nine members of the young association CMa R1. All the stars have
circumstellar dust at some distance as could be expected from their association
with reflection nebulosity. Four stars (HD~52721, HD~53367, LkH$\alpha$~220
and LkH$\alpha$~218) show H$\alpha$ emission and we argue that they are
Herbig Be stars with discs. Our photometric and spectroscopic observations
on these stars reveal new characteristics of their variability. We present
first interpretations of the variability of HD~52721, HD~53367 and the two
LkH$\alpha$ stars in terms of a partially eclipsing binary, a magnetic activity
cycle and circumstellar dust variations, respectively.
The remaining five stars show no clear indications of H$\alpha$ emission in
their spectra, although their spectral types and ages are comparable with those
of HD~52721 and HD~53367. This indicates that the presence of a disc around a
star in CMa R1 may depend on the environment of the star. In particular we
find that all H$\alpha$ emission stars are located at or outside the arc-shaped
border of the H\,{\sc ii} region, which suggests that the stars inside the arc
have lost their discs through evaporation by UV photons from nearby O stars,
or from the nearby ($ 1.4$) and unusually high mass accretion rates.
This phenomenon does not appear to be restricted to binary systems,
however, since a comparable fraction of single T Tauri stars exhibit the
same properties. These high accretion stars are probably not at an earlier
stage of evolution, as has been proposed. Their semblance of younger
protostars at optical and infrared wavelengths is most likely because of
their similar high levels of accretion, which are above the norm for T
Tauri stars, and not because of similar ages.
The stellar and circumstellar properties are also used to indirectly trace
the evolution of circumbinary material. In contrast to single T Tauri
stars, which have disk dissipation timescales comparable to their ages,
the disk dissipation timescales for binary T Tauri stars are roughly 1/10
of their ages. Replenishment of the inner circumstellar disks may be
necessary to explain the continuing disk accretion in these systems.
The longer disk lifetimes of circumprimary disks, despite
their higher depletion rates, suggests that circumprimary disks are being
preferentially replenished, possibly from a circumbinary reservoir with low
angular momentum relative to the binary. Further support for circumbinary
reservoirs comes from the observed correlated presence of circumprimary and
circumsecondary disks for binaries with separations of less than $\sim 200$
AU. The presence of disks appears uncorrelated for wider binaries.
Additionally, binaries with separations of less than $\sim$ 100 AU exhibit
a higher fraction of high mass ratio (m$_\textrm{\scriptsize
s}$/m$_\textrm{\scriptsize p}$) pairs than wider binaries.
These separation dependent properties can be explained if the components
are being replenished from a common circumbinary reservoir with low angular
momentum. The components of the closest pairs are expected to be more
equally replenished than the widest pairs, which consequently sustains both
disks and drives their mass ratio toward unity. Overall, the results of
this study corroborate previous work that suggests fragmentation is the
dominant binary star formation mechanism; disk instabilities and capture
seem unlikely.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by ApJ. }
%% If preprints are available on the WWW you can give the web
%% direction here.
{Preprint available at: http://xxx.lanl.gov/abs/astro-ph/0103098}
%\end{document}
\v5
%% Between these brackets you write the title of your paper:
{\large\bf{Millimeter continuum image of the circumstellar disk around the young star Haro 6-5B}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ S. Yokogawa$^1$, Y. Kitamura$^2$, M. Momose$^3$, Y. Asaki$^2$,
M. Tamura$^4$, S. Ida$^5$,\ and R. Kawabe$^4$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Nobeyama Radio Observatory, Nobeyama Minamimaki Minamisaku,
Nagano, 384-1305, Japan} \\
$^2$ {Institute of Space and Astronautical Science, Yoshinodai,
Sagamihara, Kanagawa, 229-8510, Japan} \\
$^3$ {Institute of Astrophysics \& Planetary Sciences, Ibaraki
University, Bunkyo 2-1-1, Mito 310-8512, Japan}\\
$^4$ {National Astronomical Observatory, Mitaka, Tokyo, 181-8588, Japan}\\
$^5$ {Department of Earth and Planetary Science, Tokyo Institute of
Technology, Ookayama, Meguro-ku, Tokyo 152-8551, Japan}
%% Here you may write the e-mail address of one or more
%% of the authors who will act as contact person for
%% preprint requests etc., for example:
{E-mail contact: yokogawa@nro.nao.ac.jp}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{ Aperture synthesis observations of dust continuum emission at 2 mm
from the class I object Haro 6-5B, made with the Nobeyama Millimeter
Array (NMA), are presented. A disklike structure which coincides with
the dark lane in the visible and near-infrared images is clearly
resolved with a small synthesized beam of 1.33 $\times$
1.21 arcsec with its position angle (P.A.) of 134$^o$. The
beam-deconvolved size of the disk is 2.33 $\times$ 0.97 arcsec
at P.A. = 138$^o$, and the total flux density is 36.7 $\pm$ 2.6
mJy. The radius and inclination angle of the disk derived from the
image are 309 $\pm$ 18 AU and 67 $\pm$ 5$^o$, respectively. By
model fitting of the spectral energy distribution (SED) of Haro 6-5B
with these values, the power-law index of the dust opacity, $\beta$,
is derived to be 1.05 $\pm$ 0.04 and the disk mass is calculated to be
$0.021 \pm 0.002{\,}M_{\odot}$. No extended emission with 1000 AU
scale is detected, suggesting that the envelope around Haro 6-5B has
been almost dissipated and that the object is a transient source from
the protostar stage to the T Tauri stage. }
% Here you write which journal accepted your paper, for example:
{ Accepted by Astrophysical Journal Letters}
%% If preprints are available on the WWW you can give the web
%% direction here.
%\end{document}
\clearpage
%% Between these brackets you write the title of your paper:
{\large\bf{Discovery of a molecular outflow, near-infrared jet and HH objects
towards \\
IRAS~06047$-$1117}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Jo\~{a}o L. Yun$^1$, Carlos A. Santos$^1$, Dan P. Clemens$^2$, Jos\'e M.
Afonso$^1$, Mark J. McCaughrean$^3$, Thomas Preibisch$^4$, Thomas Stanke$^4$, \&
Hans Zinnecker$^3$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1${Centro de Astronomia e Astrof\'{\i}sica da Universidade de Lisboa,
Observat\'orio Astron\'omico de Lisboa,
Tapada da Ajuda, 1349-018 Lisboa, Portugal} \\
$^2${Institute for Astrophysical Research, Boston University,
725 Commonwealth Avenue, Boston, MA 02215, U.S.A.} \\
$^3${Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482
Potsdam, Germany} \\
$^4${Max-Planck-Institut f\"ur Radioastronomie,
Auf dem H\"ugel 69, D-53121 Bonn, Germany}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: yun@oal.ul.pt}
%% Within the following brackets you place your text:
{
We report discovery of a new young stellar object driving a point-symmetric,
near-infrared jet and molecular outflow.
The YSO is associated with IRAS~06047$-$1117 and is embedded in a dense
molecular cloud core located southeast of Orion~A.
The jet is seen in the H$_2$ $v=1-0$ line at 2.12$\mu$m and extends over a total
length of about $\sim$\,0.4\,pc. The driving source is optically invisible and
has near-infrared colors and a spectral energy distribution consistent with a
Class~I source with an estimated luminosity of 6 L$_{\odot}$.
Two Herbig-Haro objects are seen in H$\alpha$ images located close to the
positions of maximum H$_2$ emission.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by {\it Astronomy \& Astrophysics Letters} }
%A copy of this paper is available via the World Wide Web. Connect to
http://www.oal.ul.pt/papers/IRAS06047-1117
\vspace{2cm}
\fboxrule0.02cm
\fboxsep0.4cm
\fbox{\rule[-0.9cm]{0.0cm}{1.8cm}{\parbox{16cm}
{The Star Formation Newsletter is a vehicle for fast distribution of
information of
interest for astronomers working on star formation and molecular
clouds. You can submit material for the following sections: {\em
Abstracts of recently accepted papers} (only for papers sent to refereed
journals, not reviews nor conference notes), {\em Dissertation Abstracts}
(presenting abstracts of new Ph.D dissertations), {\em Meetings}
(announcing meetings broadly of interest to the star formation
and interstellar medium community), {\em New Books} (giving details of
books relevant for the same community), {\em New Jobs} (advertising
jobs specifically aimed towards persons within our specialty), and {\em
Short Announcements} (where you can inform or request information from
the community). \\
{\bf Latex macros for submitting abstracts and dissertation abstracts
are appended to each issue of the newsletter}. \\
The Star Formation Newsletter is available on the World Wide Web at
http://casa.colorado.edu/reipurth or at
http://www.eso.org/gen-fac/pubs/starform/ .
}}}
\vspace{2cm}
\begin{center}
\fboxrule0.02cm
\fboxsep0.4cm
\fbox{\rule[-0.9cm]{0.0cm}{1.8cm}{\parbox{11cm}
{ {\Large\bf Moving ... ??}\\
If you move or your e-mail address changes, please send the editor your
new address. If the Newsletter bounces back from an address for three
consecutive months, the address is deleted from the mailing list.
}}}
\end{center}
\clearpage
\begin{center}
{\Large\em Dissertation Abstracts}
\end{center}
\begin{center}
%% Between these brackets you write the title of your thesis:
{\Large\bf{Magnetic Field Effects on the Structure and Evolution of\\
Herbig-Haro Jets}}
\vspace*{0.5cm}
%% Here comes your name
{\bf{ Adriano Hoth Cerqueira }}
%% Here you write the institute where your thesis work was conducted, e.g.:
{Thesis work conducted at: Instituto Astron\^omico e Geof\'{\i}sico,
Universidade de S\~ao Paulo, SP, Brazil}
%% Here comes your present postal address (if you are about to move and know
%% your coming address give it as well) e.g.:
{Current address: Departamento de Ci\^encias Exatas e Tecnol\'ogicas, \\
Universidade Estadual de Santa Cruz, Rodovia Ilh\'eus/Itabuna, \\
km 16, Ilh\'eus, BA, 45650-000, Brazil}
%% (if you use this part, remove %%)
%% {Address as of XX XXX 1994: }
%% Here comes your e-mail address:
{Electronic mail: adriano@quark.iagusp.usp.br}
%% Name of your adviser:
{Ph.D dissertation directed by: Elisabete M. de Gouveia Dal Pino}
%% Month and Year of thesis:
{Ph.D degree awarded: March 2001}
\vspace*{0.8cm}
\end{center}
%% IF YOU USE ANY PERSONAL LATEX COMMANDS IN YOUR ABSTRACT,
%% PLEASE INCLUDE THEIR DEFINITIONS HERE!
%% Within the following brackets you place your text:
{In this work, the structure and evolution of Herbig-Haro (HH)
jets is analyzed with the help of three-dimensional (3-D), Smoothed
Particle Hydrodynamics simulations. We have carried out the first
3-D magneto-hydrodynamics (MHD) numerical simulations of steady-state
and pulsed, radiativelly cooling jets, adopting parameters that are
suitable for HH jets in the literature (e.g., de Gouveia Dal Pino \&
Cerqueira, Astro. Lett. and Commun. 1996, 34, 303). We show that the
inclusion of the magnetic field, for which we have used different initial
configurations and intensities ($\beta = 8 \pi p/B^2 \simeq 0.1$, 1 and
$\infty$; or $B \simeq 260 \mu$G, 83 $\mu$G and 0), enhances the jet
collimation, particularly in the case of helical and toroidal fields. In
the case of steady-state simulations, we show that the appearance of
internal crossing shocks, which are excited by the MHD Kelvin-Helmholtz
(K-H) instability is inhibited when radiative cooling is taken into
account. Therefore, MHD K-H instabilities seem to play a secondary role in
the formation of internal emission knots along the jet beam of HH jets,
where the radiative cooling is very important (Cerqueira \& de Gouveia
Dal Pino 1999, ApJ, 510, 828). We show that the presence of magnetic
fields can significantly affect the morphology of the steady-state
jets close to the head (Cerqueira, de Gouveia Dal Pino \& Herant, 1997,
ApJ, L185). In particular, both the helical and the toroidal fields,
unlike the longitudinal field, can inhibit the formation of the cold,
dense structures that are found to develop in this region in purely
hydrodynamic simulations (which are due to Rayleigh-Taylor and global
thermal instabilities). We have also performed 3-D simulations of pulsed
jets. In this case, the bright emission knots observed along the HH jets
are naturally explained by the pulses which quickly steepen into double
shock structures as they propagate downstream (forming the so-called
internal working surfaces; IWS's). We show that the presence of different
magnetic field topologies in close equipartition with the gas does not
introduce relevant effects on the overall morphology of the HH jets.
However, the magnetic fields can significantly affect the detailed
structure and emission properties of the head and internal knots with
respect to purely hydrodynamic calculations, particularly for helical
and toroidal geometries (Cerqueira \& de Gouveia Dal Pino 2001a, ApJ
{\it Letters}, 550, in press). We have estimated the H$\alpha$ emission
within the knots and found that the intensity in this line could be up to
$4-5$ times larger than that found in the pure HD case. For the different
adopted magnetic field configurations, we find that the toroidal component
steepens within the IWS's, while the longitudinal component attains its
maximum intensity between the IWS's. Our simulations of pulsed jet with
an initially helical magnetic field topology show the development of
the kink mode of the MHD Kelvin-Helmholtz instability which promotes a
gentle wandering of the jet axis. Some features previously detected in
2-D MHD simulations seem to be smoothed out in the 3-D flows. For example,
we find no evidence for the appearance of the so-called nose-cones which
are often detected in two-dimensional numerical simulations involving
toroidal fields (see Cerqueira \& de Gouveia Dal Pino 2001b, ApJ,
submitted). Since there is no direct observational evidence of such
structures in the HH jets, the present findings stress the importance
of fully 3-D studies of these objects.}
%% If you have your thesis on the web, please provide the web address here
\clearpage
\begin{center}
%% If you use any personal Latex commands in your abstract, please include
%% their definitions here.
%% Between these brackets you write the title of your thesis:
{\Large\bf{Particle Splitting: A New Method for SPH Star Formation Simulations}}
\vspace*{0.5cm}
%% Here comes your name
{\bf{Spyridon Kitsionas}}
%% Here you write the institute where your thesis work was conducted, e.g.:
{Thesis work conducted at: Department of Physics and Astronomy, Cardiff University, U.K.}
%% Here comes your present postal address (if you are about to move and know
%% your coming address give it as well) e.g.:
{Current address: 14 John Kennedy str., Kesariani, GR-16121, Athens, Greece}
%% (if you use this part, remove %%)
%% {Address as of XX XXX 1997: }
%% Here comes your e-mail address:
{Electronic mail: kitsionas@fnet.gr}
%% Name of your adviser:
{Ph.D dissertation directed by: Prof. Anthony P. Whitworth}
%% Month and Year of thesis:
{Ph.D degree awarded: December 2000}
\vspace*{0.8cm}
\end{center}
%% Within the following brackets you place your text:
{\noindent Particle Splitting is a new algorithm invented for use with
self-gravitating SPH codes. It is designed to enable numerical
simulations to obey the Jeans condition at all times (but it could be
used in other contexts, to satisfy other conditions which require high
resolution locally). With particle splitting, all coarse particles in
regions of interest, are erased and replaced by sets of fine
particles, increasing the numerical resolution of the simulations. A
new algorithm for calculating smoothing lengths was added to our code,
to accommodate the mixing of different mass particles. Our particle
splitting SPH code reproduced the results of standard test
simulations. \vspace{3mm}
\noindent Simulations of rotating clouds with m=2 density
perturbations produce a binary and a bar. We confirm that
fragmentation of the bar should be attributed to inadequate
resolution. By applying Particle Splitting to such simulations, we
reproduce the results of high resolution finite difference simulations
(Truelove {\it et al}. and Klein {\it et al}.), where bar
fragmentation is absent. We obtain these results with great
computational economy. \vspace{3mm}
\noindent We apply Particle Splitting to simulations of clump-clump
collisions. We investigate the influence of clump mass, clump velocity
and collision impact parameter on the structures formed. We show that
such collisions lead to the formation of shocked layers. Networks of
filaments or spindles, and groups of protostellar discs form within
the layers. In all collisions, fragmentation of the filaments was the
common mechanism producing the groups of protostars. Low-mass
secondary companions to the protostars may form subsequently by
instabilities in the discs and/or dynamical interaction between the
protostars. However, due to time-step requirements, we cannot follow
the disc evolution for long enough to explore the formation of
secondaries. \vspace{3mm}
\noindent We show that all the protostars formed have mass accretion
rates of $\sim$5 x 10$^{-5}$ M$_{\odot}$ yr$^{-1}$ for the first 10-20
thousand years after their formation. This mechanism shows 10-20\%
Star Formation efficiency. The efficiency increases with increasing
clumps mass. Collisions with impact parameter $b < $0.4 and Mach
number $\mathcal{M} \geq$10 give the highest efficiency. We predict
the existence of filaments with $n_{H_{2}} \geq$5 x 10$^{5}$ cm$^{-3}$
in sites of dynamical Star Formation. These filaments could be
observed in NH$_{3}$ or CS line radiation, in star forming regions
lying within 1 kpc.}
\newpage
\begin{center}
{\Large\em Meetings}
\end{center}
\vspace*{0.6cm}
\begin{center}{\Large\bf Center for Star Formation Studies 2001 Summer
Workshop:\\ Star Formation in the Galactic Context}\end{center}
\begin{center}{\large Saturday, July 14 - Thursday, July 19 (lectures
start the morning of the 15th),\\ Univerisity of California at Santa
Cruz}\end{center}
{\large This workshop has a maximum capacity of 125 people. Room and
board for the 5 days costs around \$400, and there is a \$35
registration fee. There will also be a separate charge for a banquet
dinner which will be held in a local restaurant.}
\begin{center}{\large\bf To register, contact Cathy Clausen at
cclausen@natsci.ucsc.edu.}\end{center}
{\large The following is a preliminary agenda. Look for an up-to-date
schedule on the Center's web page at {\tt
www-space.arc.nasa.gov/\verb+~+csf}.}
\vspace{0.2in}
I. Nearby Star Formation, with an emphasis on the``Big Picture'' of
Galactic Star Formation.
A. Large Scale ISM Turbulence, Flows, Cloud Formation
$\bullet$ Javier Ballesteros, Mordecai MacLow, Richard Klein, Phil
Myers
B. Chemical Evolution of Molecular Material and the Dynamical
Evolution of Molecular Clouds
$\bullet$ J . Alves, P. Caselli, Malcolm Walmsley, David Wilner, John
Scalo
C. Clusters and Associations in the Solar Neighborhood
$\bullet$ Lee Hartmann (tentative), Charles Lada, Lynn Hillenbrand,
Fransesco Palla, Leonardo Testi, Michael Meyer, Fred Adams
II. Clustering of Star Formation in Different Environments
A. Globular Clusters and Super Star Clusters in Starburst Galaxies
$\bullet$ Cesar Briceno, Doug Lin (tentative), Ralph Pudritz
III. Star Formation and the ISM in low-Z Spiral/Disk Galaxies
A. Observations, Global Star Formation Rates and Correlations
$\bullet$ R. Kennicut (tentative), E. Ostriker, Frank Shu, R. Allen,
Tony Wong, Annette Ferguson
IV. Dwarf Galaxies
$\bullet$ Leo Blitz, Liese Van Zee, Eva Grebel (tentative), K.-Y. Lo
(invited), Arthur Wolfe
V. Starburst Phenomenon
$\bullet$ Dieter Lutz (invited), James Graham (invited), Timothy
Heckman, Jonathon Tan
VI. Regulated Star Formation and Feedback Processes
$\bullet$ Andrea Ferrara, Jasper Sommer-Larson (invited), Crystal
Martin, David Hollenbach
\end{document}
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%%% LaTeX MACRO FOR THE STAR FORMATION NEWSLETTER %%%
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%%% Please use for abstracts of papers which have been ACCEPTED in %%%
%%% REFEREED JOURNALS (do not send abstracts of reviews for books %%%
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%% If preprints are available on the WWW you can give the web
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%%% LaTeX MACRO FOR DISSERTATION ABSTRACTS
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%%% Please use the following macro for your thesis abstract. You
%%% have one full page for everything, and you are very welcome to
%%% go into detail with your results, so the readers get a
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%%% brackets below and mail to reipurth@casa.colorado.edu
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%% Between these brackets you write the title of your thesis:
{\Large\bf{Title of Thesis}}
\vspace*{0.5cm}
%% Here comes your name
{\bf{ Author }}
%% Here you write the institute where your thesis work was conducted, e.g.:
{Thesis work conducted at: Steward Observatory, University of Arizona, USA}
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%% Month and Year of thesis:
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